TNF .alpha. is a polypeptide of molecular weight 17500, whose primary and tertiary structure has been elucidated (Pennica, D. et al. Nature 312: 724 (1984) and Jones, E. Y. et al. Nature 338: 225 (1989)). TNF .alpha. is biologically active as a trimer. The main source of TNF .alpha. are cells of the monocyte/macrophage lineage, but after appropriate stimulation it is produced by other cell types as well (e.g. T-lymphocytes).
TNF .beta. is a polypeptide closely related to TNF .alpha.. Both molecules show a 28% homology at the amino acid level (see, Pennica, D. et al. Supra and Gray, P. W. et al. Nature 312: 721 (1984)). The main source of TNF .beta. are T-lymphocytes.
TNF .alpha. was originally described as a molecule that induces haemorragic necrosis of tumors in mice. However, after large amounts of homogeneous TNF .alpha. became available upon cloning of its cDNA, it soon became clear that TNF .alpha. mediates a large array of biological activities that allow the definition of TNF .alpha. as a mediator of inflammation. See, generally, Beutler, B. and Cerami, A., Nature 320: 584 (1986).
TNF .beta. mediates a qualitatively similar array of biological activities but quantitative differences as to the doses of TNF .alpha. or .beta. required to mediate single biological activities have been described.
TNF .alpha. plays, within the inflammatory response, a pivotal role in the host defense against invasion of the organism by noxious agents. However, under certain circumstances, like chronic or acute, systemic or localized hyperproduction, TNF .alpha. leads, in conjunction with other mediators of the inflammatory response, to a large number of pathologic conditions. Cachexia and septic shock are the best known examples (see, Beutler, B. and Cerami, A., Supra and Oliff, A., et al., Cell 50: 555 (1987). Likewise, TNF .alpha. is supposed to play a pathogenic role in AIDS (Folks, T. M., et al., Proc. Natl. Acad. Sci. USA 86: 2365 (1989)), in graft-versus-host disease (Piguet, P. F., et al. J. Exp. Med. 166: 1280 (1987)), in cerebral malaria (Grau, G. E., et al. Science 237: 1210 (1987)), rheumatoid arthritis (Brennan, F. M., et al., Lancet ii: 244 (1989)) and several other disease states.
Much less is known about the in vivo effects of TNF .beta.. Given the fact, however, that it mediates in vitro, biological activities similar to those of TNF .alpha., it can be argued that, in case of hyperproduction, TNF .beta. as well may contribute to the pathogenesis of some disease states.
These results have suggested that antibodies against TNF .alpha. and, possibly, also antibodies against TNF .beta. could be therapeutically useful in those disease states in which these polypeptides exert a pathogenic effect.
In order to be therapeutically useful antibodies against TNF .alpha. should be able to neutralize the toxic effects of TNF .alpha. in vivo. Polyclonal antibodies are easily obtainable from the serum of hyperimmunized animals. These polyclonal antibody preparations, however, are not optimal for in vivo use because
they are a mixture of antibodies containing antibodies which do not neutralize TNF .alpha., PA1 they are a mixture of antibodies containing different antibodies having different affinities for the same epitope and PA1 they are difficult to standardize in terms of potency because of lot-to-lot variations. PA1 antibody class and subclass, PA1 epitope specificity, PA1 binding affinity and PA1 in vitro and in vivo neutralizing activity.
Monoclonal antibody technology is the tool of choice to bypass these problems. It permits the in vitro production, under controlled conditions and in unlimited amounts, of monoclonal antibodies of reproducible specificity and affinity against TNF .alpha. as against every immunogenic molecule. Clearly, many different monoclonal antibodies can be obtained against one single antigen. They may vary from each other in terms of
For therapeutic use it is desirable to employ a monoclonal antibody against TNF .alpha., as against any other antigen, which has high neutralizing activity. This would allow the administration of lower doses of the monoclonal antibody in order to attain therapeutically effective levels in vivo, thus mitigating the possible, undesired side-effects caused by the monoclonal antibody.